I was thinking about this 2m J-Pole design and then I thought about a 20m
vertical using my tower and mast.
Currently, I have a 45 ft Rohn 25 topped by about 20ft of masting and a
vertical 2m antenna that is insulated from the mast. So the question is
could I make this into a 20m J-Pole?
Let's see.
For a 20 meter J-Pole on 14.275 MHz, I would need to have
a main element 49.387 ft long
a second element is 16.392 ft, and
the feedpoint should be about 1.611 ft above their common connection at the
bottom.
The two elements need to be spaced by about 1.541 ft.
To me it sounds doable.I can make up a bolt on-bracket conductive bracket
connecting the tower to the smaller element "mast" and use a pair of hose
clamps to secure the coax to the elements. I could also add insulated
stabilizing brackets above this to keep the smaller element parallel with
the tower longer element). The stabilizing insulators could be made from
pieces of 1.5 inch PVC (which is actually 1.9 inches) and a couple of long
anodized U-bolts from Radio Shack or stainless ones from Home Depot if they
have long ones to hold it all in place. The bottom conductive, bracket
could be a piece of aluminum square stock available at Home Depot and a more
U-bolts. The short element could be a series of aluminum masts and/or
tubes nested inside each other.
Anyone have any thoughts on this?
Thanks & 73!
Gordon Beattie, W2TTT
201.314.6964
From: 6meter@yahoogroups.com [mailto:6meter@yahoogroups.com] On Behalf Of
adastra_2001
Sent: Sunday, January 20, 2008 9:30 PM
To: 6meter@yahoogroups.com
Subject: [6 Meter Sked] Re: Antenna Question
I built a 2 meter "J" pole using this link
http://www.hamuniverse.com/jpole.html
I made mine out of 1/2" copper pipe and it tuned up to a 1:1 SWR no
problem, I havent done a test of balun or no balun, I imagine that it
is easy enough to coil up come coax to use as an RF choke and it's
free. I want to try an experiment with my J pole to place a chassis
mount N connector at the feed point instead of using hose clamps. I
saw it done on a website once, unfortunatly I don't have the URL any
longer. It seems to be a very forgiving design so I would not get
bent out of shape about small details. just make it out of good
conductors and make low loss connections.
-- In 6meter@yahoogroups.com <mailto:6meter%40yahoogroups.com> , "FT897"
<hobergenix@...> wrote:
>
> I am going to expierment with 6 Mtr and to get started I thought I
> would build a copper J pole. I have seen lots of plans on the
> internet.
> I have looked at the varrious J pole caculators for dimmensions. Is
> the spacing between the small element and large element critical? I
> seems to me that most of the antennas use 3/4 tube for the lower
half.
> From the plans I have see this dimmension seems to very a bit from
> one to another.
>
> Also some of the antennas use a balun made up of about 5 turns of
> RG-8. Some call it an RF Choke. Some of the plans do not use it at
> all.
> I was wondering if anybody has compared opperation with and without
> it.
>
> The two designs I was looking at building are.
>
> http://www.qsl.net/w8cwe/6meterj.html
> http://www.vk4adc.com/50MHz_JPole.htm
>
> Thanks
>
> Mike
> N6IMF
>
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